1. Field of the Invention
The present invention relates to a power transmission apparatus.
2. Description of the Related Art
In a rear wheel side power transmission system of a four-wheel drive vehicle, such as a power transmission apparatus arranged between an input shaft in a side of a propeller shaft and an output shaft in a side of a rear differential gear which executes a torque transmission from the input shaft to the output shaft, for example, there is a structure described in Japanese Patent Application Laid-Open (JP-A) No. 10-329562.
The conventional power transmission apparatus has a sub-clutch apparatus connected to the input shaft which operates according to an electric current application so as to frictionally engage, a main clutch apparatus arranged between the input shaft and the output shaft. The main clutch is frictionally engaged due to a pressing force, thereby executing a torque transmission between the input shaft and the output shaft. A cam apparatus converts a frictional engagement force of the sub clutch apparatus into the pressing force for the main clutch apparatus.
In the prior art, both of the sub-clutch apparatus and the main clutch apparatus are connected to the input shaft. Both of a drive side clutch plate of the sub clutch apparatus and a drive side clutch plate of the main clutch apparatus rotate together with the input shaft when the sub-clutch apparatus is set in a non-engagement state in which an electric current is not applied, so that inertial loss becomes great.
An object of the present invention, in a power transmission apparatus having the sub-clutch apparatus and a main clutch apparatus, is to reduce inertial loss when the sub-clutch apparatus is in a non-engaged state.
According to the present invention, there is disclosed a power transmission apparatus arranged between an input shaft and an output shaft, so as to execute torque transmission.
A sub-clutch apparatus is arranged between the input shaft and an intermediate rotary body and is operated by an electric current application so as to be frictionally engaged, thereby executing a torque transmission between the input shaft and the intermediate rotary body.
A main clutch apparatus is arranged between the intermediate rotary body and the output shaft which is frictionally engaged according to a pressing force, thereby executing a torque transmission between the intermediate rotary body and the output shaft.
Also, a cam apparatus converts the frictional engagement force of the sub-clutch apparatus into the pressing force for the main clutch apparatus.